1. Field of the Invention
The present invention relates to a technology for producing a color conversion profile for use in printing.
2. Description of the Related Art
In recent years, the use of ink-jet printers and laser printers as color printers has become widespread. A color printer uses a color conversion lookup table to convert input color image data into amounts of inks of a plurality of types. In the conventional method for producing a color conversion lookup table, (i) a large number of color patches are printed, (ii) colors of the color patches are measured to obtain calorimetric values, and (iii) a lookup table that represents correspondence relationships between the colorimetric values of color patches and the amounts of ink used to print the color patches is produced.
However, calorimetric values are dependent upon viewing conditions during colorimetry. Accordingly, even when a color conversion lookup table has been produced so as to give a printout having good color reproduction under a certain viewing condition, printouts produced using the color conversion lookup table sometimes cannot achieve good color reproduction under other viewing conditions. Accordingly, there has existed a need for a color conversion lookup table that enables good color reproduction under various viewing conditions. There has also been a need, for example, when producing a copy of a painting, to produce a color conversion lookup table that can reproduce as faithfully as possible the color appearance of the original.
Further, the quality of printouts produced using a color conversion lookup table is greatly dependent upon the ink amount and calorimetric values defined in the color conversion lookup table. Actually, it is necessary to produce a color conversion lookup table so that good color reproduction can be achieved under various viewing conditions and at the same time a printout with high image quality can be obtained. Accordingly, as mentioned hereinabove, there has been a need to produce a color conversion lookup table that ensures good color reproduction under various viewing conditions and at the same time enables printing of high-quality images. Such requirements are not limited just to color conversion lookup tables, but are generally common for various types of profiles used for color conversion.
Thus, as described above, a color conversion lookup table has to satisfy simultaneously a large number of different requirements, but the required properties can differ depending on printing application, conditions during printing, and user's needs. Accordingly, a system is needed that can easily produce an adequate profile corresponding to printing application or conditions during printing and makes it possible to select an adequate profile according to printing application or conditions during printing from among a large number of profiles.
Further, while it is desirable to produce an adequate profile that reflects the results obtained in simultaneous evaluation of a large number of different properties according to printing application, conditions during printing, and user's needs, as described hereinabove, the increase in the number properties that have to be evaluated will predictably make it impossible to produce a profile rapidly. In particular, in evaluating the image quality, quantification corresponding to viewer's vision has to be performed and such quantification requires complex computations. Accordingly, there has been a need for a system that can produce a profile rapidly and easily, while efficiency evaluating the image quality.